The present invention relates to power converters. Specifically, the present invention is a board mountable power supply having a multi-function control pin.
More and more electronic applications are requiring distributed power architectures where the current requirements of the electrical loads are requiring the power supplies to be moved as close to the load as practicable. Instead of the single power supply which would accept ac line voltage and produce a dc or ac output voltage for use by an entire electrical system, today""s ultra fast electronics and electrical components require their own power supply to accommodate the high transients in their load currents. This new concept in power systems is often referred to as a xe2x80x9cdistributed power architecture.xe2x80x9d This type of power architecture can be implemented by means of a system rectifier that converts the ac line current into an unregulated or slightly regulated dc voltage, and numerous xe2x80x9cpoint-of-loadxe2x80x9d power supplies. The point-of-load power supplies accept the dc voltage from the rectifier and produce a highly regulated dc voltage which is able to accommodate very large current transients (large di/dt).
The point-of-load power supplies need to be small, have a high power density, and be mountable on the circuit boards near the load. In addition, the point-of-load power supplies should be modular to allow two or more to be connected in parallel to supply power to high current loads, or to provide redundancy. This modularity allows a single design to be adapted for loads with varying current requirements. These small modular power supplies, however, present numerous design issues. Their high power density and small size, force pin footprints to be minimized, and when placed in parallel they must be forced to share current effectively.
The small size and high power density requirement forces the power modules to sacrifice features both due to lack of space on the circuit board as well as to minimize the number of pins, as well the pin footprints, so that the modules take up as little space as possible on the system board to which they will be mounted. Further, small variances in component values or reference levels will cause one or two paralleled power supplies to supply the majority of load current while some of the remaining modules supply relatively little, or no, current. This disparity in load currents causes the modules supplying the majority of the current to wear faster due to the increased thermal stresses, leading to premature failures in the field.
Accordingly, what is needed is a power supply module that minimizes the pin footprint and shares current effectively when placed in parallel with other power supply modules.
The present invention provides a power supply module with a multifunction control pin which allows the module to be disabled, the output voltage to be trimmed and the current between parallel modules to be shared more equally. The power supply module of the present invention is formed by a power train and a controller. The power train accepts an input voltage and produces a regulated output voltage capable of powering a load. The power train includes an input voltage pin, an output voltage pin and a common pin for connecting between the input voltage and the load. The controller is connected to the power train and operates to control the power train to maintain the output voltage at its regulated level despite changes in the input voltage or load current requirements. The controller includes the multifunction control pin as well as an internal reference voltage which is used to set the output voltage.
The multifunction control pin allows the output voltage to be trimmed by allowing the reference voltage used by the controller to be adjusted up or down. The multifunction control pin is capable of disabling the power supply module by either reducing the reference voltage to zero, or by disabling an internal integrated circuit in the controller itself. Additionally, the multifunction control pin can provide for improved current sharing between paralleled power supply modules. Since differences in the internal reference voltages between power supply modules is a major source of current sharing deficiencies, interconnecting the multifunction control pin of each of the parallel power supply modules sets the reference voltage in each module to the same value and allows the parallel power modules to share current much more equally.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art will appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.